An ultrasonic diagnostic apparatus is an apparatus for picking up a diagnosis image on the basis of an echo signal output from an ultrasonic probe and a reflection signal thereof. Plural ultrasonic oscillators are arranged in the ultrasonic probe. The ultrasonic oscillator converts a driving signal to an ultrasonic wave and transmits the ultrasonic wave to an examinee, and also it receives a reflection echo signal generated from the examinee and converts the reflection echo signal into an electrical signal.
A broad-band ultrasonic probe using cMUT chip has been recently developed. The cMUT chip is a hyperfine capacitance type ultrasonic oscillator manufactured by a semiconductor microfabrication process (for example, Patent Document 1).
In an example of the structure of a backing layer of this type of ultrasonic probe, the acoustic impedances of the backing layer and the cMUT chip are matched with each other in order to suppress unnecessary vibration of an electrode at the backing layer side in the cMUT chip (for example, Patent Document 2).
Patent Document 1: U.S. Pat. No. 5,894,452
Patent Document 2: U.S. Pat. No. 6,714,484